1. Field of the Invention
The present invention relates to a tandem type image forming apparatus including a plurality of photosensitive drums.
2. Description of the Related Art
Image forming apparatuses such as printer, copying machine, include a photosensitive drum and a developing device. In view of the fact that endurance limit or service life is not the same in the photosensitive drum and the developing device, the photosensitive drum and developing unit are individually detachably mounted on the image forming apparatus to enable a user to replace the used photosensitive drum or developing unit with a new one.
Japanese Patent Application Publication No. 2004-94151 discloses a color printer including a plurality of photosensitive drums, a plurality of developing devices, and a transfer belt unit. The photosensitive drums are mounted from the upper portion of the printer and placed on the frame of the transfer belt so as to confront the corresponding developing devices. When one or more developing devices are replaced with new ones, the transfer belt unit is pivotally moved upward to thereby separate the photosensitive drums from the developing devices, and then the developing device is removed.
However, with the configuration disclosed in Japanese Patent Application Publication No. 2004-94151, after separation of the photosensitive drums from the developing devices, almost all part of the photosensitive drum is exposed. Accordingly, attention has to be paid in exchanging the drum so as not to touch the photosensitive drum. Further, the photosensitive drum separated from the developing device still remains in contact with the transfer belt unit. Accordingly, the drum replacing operation has to be performed so as not to damage the photosensitive drum and the transfer belt unit.